RF switches are used in a variety of RF circuits to implement various functions. For instance, an RF system using different signaling methods over different frequencies may be implemented by using a network of antenna switches to select from between different types of RF front-end circuits. One example of such a circuit is a multi-standard cellular telephone that can make calls using different standards such as code division multiple access (CDMA) or Global System for Mobile Communications (GSM). By using an RF switch, an RF front end circuit optimized for CDMA communication may be used for CDMA calls, while an RF front-end circuit optimized for GSM communication may be used for GSM calls. In addition, RF switches may be used to implement adjustable matching networks for antennas and power amplifiers, and to provide adjusting tuning for high frequency filters by switching in and out and/or bypassing passive matching and tuning elements.
One of the key measures of performance of an RF switch is linearity, which is commonly expressed, for example, in terms of harmonic distortion and/or intermodulation distortion. In multi-band systems that both transmit and receive, appreciable distortion may degrade the performance of the RF system. For example, the harmonic or intermodulation distortion of a transmitted signal may fall in the same band of a received signal and interfere with the received signal. As such, RF switches are often specified to have very low distortion. As RF switches become more integrated and implemented on fine geometry processes, it becomes more challenging to meet high linearity performance.